Micro Channel Architecture

The Micro Channel Architecture (MCA; German microchannel ) is a proprietary bus system from IBM with up to 32-bit bus width and 10 MHz bus clock. It was found in 1987 in PS/2-Personalcomputern, but also in RS/6000 workstations AS/400-Minicomputern and even some System/370-Großrechnern ( mainframes ).

The MCA bus tried to solve the problems of the first IBM AT bus, which is known under the designation ISA bus today:

• Higher data throughput (theoretically 66 Mbytes / s )
• Shared interrupt lines
• Support for multiple bus master DMA
• Configuration register
• Processor independence
• Automatic card detection
• Improved electrical properties

MCA is incompatible with all other bus systems.

One motivation IBM to develop its own bus system, was the recovery of the expansion-card market.

The MCA bus, however, has over the other bus systems in the market can not enforce, since only few and very expensive tickets were available and older ISA cards could not be used. Manufacturer of MCA cards also had to purchase an expensive license from IBM. With the PCI bus MCA almost disappeared from the market.